In connecting two pipes together, it is often advantageous to counterbore one pipe end so that it can be appropriately matched with the end of another pipe end to facilitate proper welding of the two pipe ends together. Precision and accuracy are desired when counterboring pipe ends. The machining device must be held firmly in relation to the pipe in order to achieve these results. Further, in many instances a pipe in the field is out of round due to rough handling or manufacturing defects. Also, weld seams along the length of the pipe may provide an irregular surface. It is desirable that the machining tool follow the inner surface of the pipe with high precision to ensure uniform machining of a counterbore.
U.S. Pat. No. 5,171,110 to Pettifer et al. (the Pettifer '110 patent) discloses one such machining tool that rotates a cutting tool against the inside circumferential surface of the pipe end and advances it axially into the pipe until a counterbore has been formed. In the Pettifer '110 patent, the cutting tool is pivotally connected to a rotating flywheel and the cutting tool is pressed radially outward against the inside surface of the pipe by being rotated about its pivot point. Thus the cutting tool of the Pettifer '110 patent follows the inside contour of the pipe by oscillating arcuately about its pivot point. The Pettifer '110 patent discloses a single actuator which pivots the cutting tool about its pivot point.
It has been found that a need exists for an improvement in the device of the Pettifer '110 patent which will provide an improved adjustment of the radial extent of the cutting tool during operation as well as provide improved forcing of the cutting against the inside surface of the pipe. The present invention provides a marked improvement over the cutting tool control of the invention of the Pettifer '110 patent.